student research day - Case Western Reserve University School of ...

Kathryn Martires
Factors that Affect Skin Aging: a Cohort-based Survey on Twins
Kathryn Martires, Dr. Pingfu Fu, Dr. Amy Polster, Dr. Kevin Cooper and Dr. Elma Baron
Dermatology; Epidemiology and Biostatistics
University Hospitals Case Medical Center, Case Western Reserve University
Introduction: Photoaging describes a phenomenon brought about by long-term sun exposure that causes
inflammatory skin changes, resulting in photodamage and premature skin aging. The topic has become an issue of
great importance and expense. In 2005, $160 billion were spent on aging-reversal procedures. More importantly,
the presence of photodamage is also related to the development of skin cancers, warranting investigation into the
etiology and prevention of photodamage.
Objective: This study identifies environmental factors that correlate with skin photoaging, controlling for genetic
susceptibility by using a questionnaire administered to pairs of twins at the annual Twins Days Festival in
Twinsburg, Ohio.
Methods: The survey collected information about degree of sun exposure, sun protective behaviors, history of skin
cancer, smoking and drinking habits, and body mass index from a cohort of twins. Clinicians then assigned a
Fitzpatrick type and clinical photodamage score to each participant. Univariate analysis examined associations
between each variable and photodamage, using the Spearman correlation coefficient and the Kruskal-Wallis test.
For factors found to be significant in univariate analysis, multivariable linear regression with the forward model
selection procedure was used to determine independent associations. All tests were two-sided and p-values less
than 0.05 were considered significant.
Results: Factors found to positively predict photodamage include cigarettes smoked, with a correlation coefficient
(r) of 1.62 (p=0.0004), skin cancer history with r=1.62 (p= 0.045), and weight with r=0.45 (p=0.008). Factors
negatively correlated with photoaging include Fitzpatrick type with r=-0.47 (p=0.0004), and sun screen use with
r=-0.31 (p= 0.007).
Conclusions: The study of twins provides a unique opportunity to control for genetic susceptibility in order to
elucidate environmental influences on skin aging. The relationships found between smoking, weight, sunscreen
use, skin cancer, and photodamage in these twin pairs may help to motivate the reduction of risky behaviors.
Supported by University Hospitals Case Medical Center Department of Dermatology
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